DE69104344T2 - Process for the preparation of alkyl aromatic compounds with a solid catalyst. - Google Patents

Description

Alkyl aromatic compounds form important chemicals that can be used as intermediates in many industrial applications such as polymeric material, plasticizers, detergents, etc. To date, the preparation of alkyl aromatic compounds has been carried out by alkylating an aromatic compound with an alkylating agent in the presence of acid catalysts. These acid catalysts include sulfuric acid and hydrofluoric acid due to their relatively good activity for the intended purpose. However, the use of these liquid acids such as sulfuric acid or hydrofluoric acid has some inherent disadvantages or problems. The above acids are extremely corrosive in nature and thus require special handling and facilities due to their hazardous nature. In addition, the use of these acids could also involve some environmental problems accompanying them. Therefore, it would be preferable to use a safer and simpler catalyst, preferably in solid state, in a fixed bed reactor to produce the desired compounds. Using a simpler process would result in lower capital costs and therefore enable the producer to deliver a cheaper product.

In view of this, it has now been found that a solid alkylation catalyst can be used to effect the desired alkylation and thus obtain an alkyl aromatic product which has the same quality as those products obtained when using liquid acid catalyst, while also improving the activity of the catalyst and the selectivity of the product.

Previous patents have described the use of solid catalysts comprising clays containing a metal component. For example, U.S. Patent 4,499,319 describes a cation-exchanged layered clay in which a layered clay having a foliated structure is ion-exchanged with a metal cation. The catalyst is then activated by heating in air to a temperature in the range of 80 to 200°C. The catalyst can be used to alkylate aromatic compounds with an alkylating agent containing less than about 6 carbon atoms. U.S. Patent 4,749,808 also uses a metal cation-exchanged clay to produce an ester by reacting an olefin or an olefin oxide with a carboxylic acid. U.S. Patent Nos. 3,849,597 and 4,605,806 both use hydrogen ion exchanged layered clays as catalysts to produce esters in a similar manner to that set forth in the patents listed above.

U.S. Patent 3,962,361 uses an ion-exchanged synthetic saponite clay for acid-catalyzed reactions in which the clay is ion-exchanged with a metal cation and activated by heating to a temperature less than 200 ºC. Likewise, U.S. Patent 3,965,043 similarly describes an ion-exchanged natural clay for use in the alkylation of aromatic hydrocarbons similar to the above-referenced patent. Other U.S. Patents describing alkylation catalysts which are solid in nature include U.S. Patents 3,979,331, 4,046,826 and 4,075,126. These patents describe the alkylation of aromatic compounds with a synthetic clay which has been cation-exchanged and activated.

Many of these prior patents use clays that have undergone a process in which a metal cation is exchanged for the hydrogen ions normally present in the clay. The catalyst of the present invention comprises a clay that is co-extruded with a multivalent rare earth metal component rather than having the metal ion exchanged thereon. This catalyst has excellent properties in terms of the activity of the catalyst as well as in terms of the selectivity of the product obtained by the reaction.

This invention relates to a process for producing alkyl aromatic compounds and a catalyst which can be used to effect the desired reaction. Alkyl aromatic compounds can be used in many and diversified industrial applications. For example, one of the major problems encountered in population centers throughout the world is the disposal of municipal waste water containing detergents dissolved therein. Such disposal problems are particularly prevalent where the detergents comprise branched chain alkyl aromatic compounds. These branched chain detergents produce persistent foams in hard or soft water in such large quantities that the foam tends to block waste water treatment facilities and destroy the bacteria required for proper waste water treatment. These undesirable foams are found in many rivers, streams, lakes, etc. which provide a water supply to the above-mentioned population centers. The presence of these undesirable foams is in many cases due to the use of detergents that are not biodegradable and are not broken down by the action of bacteria on them. This lack of biodegradability of detergents is due to the fact that the alkyl side chain of the molecule is in many cases highly branched and therefore not easily attacked by organisms that would normally destroy the molecules. In contrast, the presence of straight-chain alkyl substituents on the ring allows bacteria to act on the alkyl chain and destroy the detergents, minimizing the formation of foams that then do not accumulate on the surface of the water or throughout the water.

By using the catalytic composition of the present invention, it is possible to produce straight-chain alkylaryl detergents due to the excellent selectivity properties of the catalyst, particularly with respect to alpha-olefins, to obtain the desired alkyl aromatic product. As will be shown in more detail below, it is possible to obtain an alkylation process in which the activity of the catalyst is maintained for a relatively long period of time and a selective product is obtained from the reaction by using the specific catalytic composition of the present invention.

It is therefore an object of this invention to provide a new catalytic composition which can be used to effect alkylation of aromatic compounds.

Another object of this invention is to provide a process for preparing such a catalytic composition and also to provide the necessary process for producing an alkyl aromatic compound.

FR-A-2 371 961 describes a catalyst suitable for the vapor phase reaction of nitrogen oxides with ammonia to form nitrogen and water, the catalyst comprising a transition metal (including, for example, cerium) on a mixture of titanium oxide and a clay.

EP-A-0 353 813 describes a process for the catalytic alkylation of benzene in the presence of an aluminum-magnesium silicate catalyst.

GB-A-2 090 766 describes a porous hydrotreating catalyst comprising a mixture of halloysite with another fibrous clay (e.g. attapulgite), optionally with a binder (e.g. alumina) and optionally with a transition metal, e.g. from Group VIB or VIII or a rare earth metal.

One embodiment of this invention provides an alkylation catalyst composition prepared by co-extruding a clay component with 0.5 to 10 wt.% of at least one multivalent rare earth metal component, drying and calcining the resulting extrudate. The clay is montmorillonite, kaolin or bentonite, and is mixed with 5 to 50 wt.% of an alumina binder prior to extrusion.

Another embodiment of this invention provides a process for preparing a catalyst composition as defined above which comprises adding an aqueous solution containing the polyvalent rare earth metal to a clay dough mixed with 5 to 50 wt.% of an alumina binder, extruding and drying the resulting mixture, and calcining the mixture.

Another embodiment of this invention provides a process for preparing an alkyl aromatic compound which comprises reacting an aromatic compound with an alkylating agent selected from olefins, alkyl halides and alkyl alcohols in the presence of a catalyst composition as defined above.

The present invention relates to a catalyst useful in the alkylation of aromatic compounds, and in particular to a catalyst composition having excellent properties with respect to the activity and selectivity of the alkyl aromatic compound formed during the reaction. In addition, the invention also relates to a process for producing an alkyl aromatic compound using the catalyst described in detail below.

The catalytic composition of the present invention comprises a mixture of clay and alumina binder and at least one multivalent rare earth metal. The mixture is extruded, dried and calcined to form the desired catalyst.

As used herein, the term "polyvalent rare earth metal" means one or more of the fifteen elements of Group III of the Periodic Table of the Elements (IUPAC) with atomic numbers 57 through 71, including lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and mixtures thereof. These elements are also known as "lanthanides" and are typically derived from monazite and bastnasite minerals. The preferred elements of this series are lanthanum and cerium, with cerium having superior performance in most cases.

The above-mentioned metals are mixed with a clay selected from bentonite, montmorillonite and kaolin. The polyvalent rare earth metal or mixture of polyvalent rare earth metals will be present in the catalytic composition in an amount ranging from 0.5 to 10% by weight of the catalytic composition.

The catalytic composition of the present invention can be prepared by mixing an aqueous solution containing at least one polyvalent rare earth metal with a mixture of alumina and clay of the type described in detail above to form an extrudable dough-like mass. Some representative examples of water-soluble salts of rare earth metals are the acetates, chlorides, nitrates, sulfates and similar salts such as lanthanum bromide, lanthanum chloride, lanthanum acetate, lanthanum nitrate, cerium bromide, cerium nitrate, etc., or mixtures thereof.

The mass is extruded to obtain an extrudate of predetermined shape, which may be in the form of pellets, spheres, etc., which is then subjected to an evaporation or drying step in which the aqueous portion of the soluble salt is removed, this step being carried out at temperatures ranging from ambient temperature (20 to 25 ºC) to 100 ºC. After the drying step, the impregnated clay is then subjected to a calcination step in which the composition is heated to a temperature in the range of 300 to 800 ºC for a period of time ranging from 1 to 24 hours. Calcination of the composition can be effected in an atmosphere of air or in an atmosphere of air containing 1 to 20% water vapor.

The clay is mixed with 5 to 50% by weight of an alumina binder. This mixture is then treated with the aqueous solution containing at least one polyvalent rare earth metal to form an extrudable mass which is then extruded through a suitable die and then subjected to drying and calcination steps similar to those described in the above paragraphs. By extruding a somewhat impregnated clay, the impregnation of the clay begins with the mixing of the aqueous solution of the clay and continues during extrusion to finally be completed after drying and calcination. It is possible to produce the desired alkylation catalyst in a more economical manner. The process is made more economical because, when preparing the catalyst in a conventional manner, such as by calcining a clay followed by impregnation, drying and calcination, it is possible to eliminate a calcination step and a separate impregnation step. Therefore, a cheaper plant is used with the result of saving costs in the production of the desired catalyst.

The alkylation of aromatic compounds using the catalytic composition of the present invention can be effected in any suitable manner, either batchwise or continuously. The aromatic compounds which are treated with an alkylating agent include either monocyclic or polycyclic compounds. In addition, the aromatic compounds can also contain substituents on the ring, examples of the aromatic compounds being benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, naphthalene, isomeric methylnaphthalenes, isomeric ethylnaphthalenes, anthracene, chrysene, pyrene, etc. Alkylating agents used as the second component in the process include olefins containing 2 to 20 carbon atoms, alkyl halides, alcohols, etc. Some specific examples of these alkylating agents are ethylene, propylene, the isomeric butenes, pentenes, hexenes, heptenes, octenes, nonenes, decenes, undecenes, dodecenes, tridecenes, tetradecenes, pentadecenes, hexadecenes, heptadecenes, octadecenes, nonadecenes, eicosenes, etc., methyl chloride, ethyl chloride, propyl chloride, butyl chloride, hexyl chloride, octyl chloride, decyl chloride, dodecyl chloride, tetradecyl chloride, methyl bromide, ethyl bromide, propyl bromide, butyl bromide, heptyl bromide, nonyl bromide, undecyl bromide, etc., methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, etc. It is also contemplated that mixtures of olefins may be used as alkylating agents. It is to be understood that the aromatic compounds and alkylating agents mentioned above are only representative of the types of compounds that can be used as reactants in the alkylation process and that the present invention is not limited to these compounds.

The alkylation reaction can be carried out batchwise by adding the aromatic compound and alkylating agent to a suitable apparatus such as a rotary or mixing autoclave together with the catalytic composition. In the preferred embodiment of the invention, the alkyl aromatic compound is present in the reaction mixture in an excess of alkylating agent, preferably in the range of 2:1 to 20:1 moles of aromatic compound per mole of alkylating agent. The reactor is sealed and heated to the desired operating temperature, which may be in the range of 80° to 200°C. To effect the reaction preferably in a liquid phase, pressurization is also carried out to maintain an operating pressure in the range of 200 to 1000 psig (1482 to 7000 kPa). The operating pressure employed can be generated by the introduction of an inert gas such as nitrogen, helium, argon, etc., when the alkylating agent is in liquid form. Conversely, when the alkylating agent employed is in gaseous form, a portion of the operating pressure can be generated by the autogenous pressure of the gaseous alkylating agent, while the remainder is generated by the presence of an inert gas. After completion of the reaction time, which can range from 0.5 to 4 hours or more, heating is discontinued and after the reactor and its contents have returned to room temperature, excess pressure is relieved, the autoclave opened and the reaction mixture recovered therefrom. The desired alkylaromatic compound can then be separated and recovered from unreacted starting materials by conventional means such as fractional distillation.

When the alkylation reaction of the present invention is effected in a continuous manner, an amount of the catalytic composition is charged to a reactor, which may be tubular in shape. The reactor is heated to the desired operating temperature and brought to the desired operating pressure, after which the reactants, comprising the aromatic compound and the alkylating agent, are continuously passed over the catalyst bed at a predetermined liquid hourly space velocity. After passing through the catalyst bed for a predetermined period of time, the reactor effluent is continuously withdrawn and subjected to conventional separation means whereby the desired alkyl aromatic product is separated and recovered, while unreacted starting materials may be recycled to the reactor to form part of the feed.

If the catalytic composition of the present invention is solid in nature, various types of continuous operation can be used. For example, the catalyst may be maintained in the reactor as a fixed bed while the aromatic compound and alkylating agent are passed through the bed in either an upflow or a downflow. Alternatively, a moving bed operation may be employed in which the catalyst bed and reactant are passed through the reactor either cocurrently or countercurrently to each other. Similarly, a slurry operation may be employed in which the catalyst is carried into the reactor as a slurry in one or both of the reactants.

The following examples serve the purpose of illustrating the novel catalytic compositions and process of the present invention.

Example I (comparative example)

A catalyst not according to the present invention was prepared by mixing 750 g of a clay known commercially as Filtrol 113, which is a montmorillonite type clay, with sufficient of an aqueous solution of cerium nitrate to provide 2.8% cerium on the finished catalyst. The resulting paste or dough was extruded through a die to form 0.8 mm (1/32 inch) extrudates. After drying at a temperature of 90°C, the extrudate was calcined in an air atmosphere containing 10% water vapor at 600°C for 2 hours. This catalyst was designated A.

Example II

In a similar manner as set forth in Example I above, a catalyst of the present invention was prepared by forming a mixture containing 80% of a clay known commercially as Filtrol 13 with 20% alumina. The mixture was treated with sufficient aqueous solution of cerium nitrate to give a 3% by weight amount of cerium in the finished catalyst. The resulting dough was extruded through a die to give 0.8 mm (1/32 inch) extrudates. The extrudates were dried and calcined in an air atmosphere containing 10% water vapor for 2 hours at a temperature of 600°C. This catalyst was designated B.

Example III (comparative example)

A third catalyst not according to the present invention was prepared by extruding a dough of Filtrol 113 to form 0.8 mm (1/32 inch) extrudates which were dried and calcined in an air atmosphere containing 10% water vapor at 600°C for 2 hours and this catalyst was designated Catalyst C.

Example IV (comparative example)

A fourth catalyst not according to the present invention was prepared by producing a doughy paste comprising 80% Filtrol 13 and 20% alumina. The paste was extruded through a die to form 0.8 mm (1/32 inch) extrudates, which were then calcined in an air atmosphere containing 10% water vapor at 600 ºC for 2 hours. This catalyst was designated Catalyst D.

Example V

The four catalysts were used in an alkylation reaction by placing 25 cc of each catalyst in 12.7 mm (1/2 inch) inside diameter stainless steel tubular reactors. A feed comprising a mixture of benzene and an alkylating agent consisting of a mixture of olefins containing 10 to 14 carbon atoms in a benzene to olefin ratio of 8:1 was fed to the reactor at a liquid hourly space velocity of 2.5 hr-1. The reactor was maintained at a temperature of 150°C under a pressure of 500 psig (3550 kPa). The product recovered from the reactor was analyzed to determine percent olefin conversion, percent detergent alkylate selectivity and percent linearity. The results of these analyses are summarized in the table below. Olfin Conversion, % Detergent Alkylate Selectivity, wt% Percent Linearity

From the above table it can be seen that the detergent alkylate selectivity, which is defined as the weight of total monoalkylbenzenes divided by the total weight of all products including dialkylbenzenes, olefinic oligomers and monoalkylbenzenes, is greater in all cases where the catalysts (Catalysts A and B) contain a polyvalent rare earth metal as compared to the catalysts not containing the metal. This therefore clearly shows that the presence of a polyvalent rare earth metal with the clay results in a greater amount of a desired product being obtained which comprises a monoalkylbenzene which can then be used as an intermediate in the manufacture of biodegradable detergents. Catalyst A is not an example of the invention.

Claims (9)

1. An alkylation catalyst composition prepared by co-extruding a clay component and from 0.5 to 10 wt.% of at least one multivalent rare earth metal component, drying and calcining the resulting extrudate, wherein the clay is montmorillonite, kaolin or bentonite and is mixed with 5 to 50 wt.% of an alumina binder prior to extrusion. 2. Composition according to claim 1, characterized in that the polyvalent rare earth metal is lanthanum or cerium. 3. A process for preparing a catalyst composition according to claim 1 or 2, which comprises adding an aqueous solution containing the polyvalent rare earth metal to a dough of clay mixed with 5 to 50% by weight of an alumina binder, extruding the resulting mixture, and drying and calcining the mixture. 4. Process according to claim 3, characterized in that the mixture is calcined at a temperature of 300 to 800 °C. 5. A process for preparing an alkylaromatic compound by reacting an aromatic compound with an alkylating agent selected from olefins, alkyl halides and alkyl alcohols in the presence of a catalyst, characterized in that the catalyst is a composition according to claim 1 or 2. 6. Process according to claim 5, characterized in that the alkylation is carried out at a temperature of 80 to 450 °C and a pressure of 446 to 13,900 kPa. 7. Process according to claim 5 or 6, characterized in that the aromatic compound and the alkylating agent are used in a molar ratio of aromatic compound to alkylating agent in the range of 2:1 to 20:1. 8. Process according to one of claims 5 to 7, characterized in that the aromatic compound is benzene. 9. Process according to one of claims 5 to 8, characterized in that the alkylating agent comprises a mixture of olefinic hydrocarbons having 9 to 15 carbon atoms.